The present invention relates to the protection of detector-fitted cameras against jamming, dazzling or even destruction by what may be called optronic countermeasures.
In the field of optronic countermeasures, there is a known method of detecting a camera through the reflection of the beam of a continuous low-powered laser, and then aiming a power laser that gives pulses towards the camera that has been localized, to illuminate all or a part of its optical detector in order to dazzle or even damage it. To this end, the two lasers work at a wavelength for which the optical system of the camera is transparent.
The dazzling of the camera by the beam of the power laser is due to a saturation of all or a portion of the sensors that constitute the detector, and results in images having a surface that is partially or totally saturated. If the frequency of the pulses of the laser is greater than the frequency of the images, then this saturation systematically affects all the images.
A known way of protecting a camera against these countermeasures is to identify the monochromatic radiation of the lasers by discrimination between the narrow spectrum of this radiation and the wide spectrum of the natural sources and to stop the frame scanning of the camera or inhibit its amplification circuits throughout the duration of the pulses of the disturbing laser. To have a loss of image corresponding substantially to that part of the image alone which is concerned by the laser pulse, it is difficult to eliminate only that part of the scanning frame which is disturbed, and in the so-called second-generation cameras, namely cameras where the detection is immediately followed by a multiplexing operation with a single amplifier at the output of the multiplexer, it is difficult to inhibit the amplifier solely during the passage of the disturbed signals.